It is narrated from Abu al-Zubayr (may Allah have mercy on him) that he said: Ata (may Allah have mercy on him) instructed me to ask Sa'id (bin Jubayr) (may Allah have mercy on him) where the hands should be in prayer: above the navel or below the navel? So I asked him, and he said: Above the navel.
Abu Mijlaz Lahiq bin Humayd said the same. The most authentic report narrated in this chapter is the report of Sa'id bin Jubayr and Abu Mijlaz. It has been narrated from Ali (may Allah be pleased with him) that it is below the navel, but there is weakness in its chain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2340